Thursday, July 2, 2009

Probabilities when Drawing

I was rereading one of Jackalware's blog entries about probabilities in Guardians, and I decided I was going to do the math on this one for myself. Yes, I've been away from teaching for less than one week, and already I'm doing recreational mathematics.

Anyway, my numbers were way off. I thought I was doing it right, but I must've been entering something incorrectly. I finally gave up and used the formula that Excel has just for this sort of thing, and which Jackalware originally used as well.

Here's what the results look like:

How do you read this?

The "60" in the upper left is the number of cards in the deck.

The rest of the numbers in column A represent how many of card "X" you have in the deck (terrain, shields, Vampires, Knights, etc.).

The rest of the numbers in row 1 represent how many you may get in your initial 12 card draw.

The formula is shown. Note the dollar signs ($). They are important for cutting and pasting in Excel. Don't forget them. Notice that $A$1 has two of them. Doubly important.

You can expand the list by adding more rows and columns and copying & pasting the formula into more cells. It you paste into an invalid cell (e.g., drawing 3 copies of a card when there are only 2 in the deck), you will get an error.

The formula has a 12 in it. That stands for the 12-card draw.You can adjust this for other card games (do you play other card games?) just by changing that number.

How NOT TO read this

Let's say you have 8 Shields and 8 Terrain in a deck of 60 cards.There is a 33.66% chance of getting 2 Shields in the initial draw.There is a 33.66% chance of getting 2 Terrain in the initial draw.There is NOT a 67.32% chance of getting 2 Shields and 2 Terrain!Nor if there a (33.66*33.66)% chance. (In other words, don't add or multiply).

It's a little more complicated than that. The chart just gives you a basic idea, such as if you put 8 in your deck, you are most likely to get 1 or 2. If you put 10 in your deck, you are likely to get 2 or 3.

If you 5 each of 8 creatures, you will most likely get 1 of any specific one, but you could easily get 2 of some and none of the others.

Welcome to Tanniker Smith's Guardians Page

The material in this web log is related to the Guardians trading-card game, formerly published by FPG, Inc. in the mid-90s. It was a fun, wacky game that raised the bar for artwork in card games. It was also a great strategy game that was discontinued way too soon.

Much of the material on this website has been previously published by me in other forms: on Usenet, the Yahoo mailing list group or on an older Guardians website that will be going away soon, if it hasn't already.